Alkaloid monomers, liquid crystal compositions and polymer networks derived therefrom

ABSTRACT

Disclosed is the chemical synthesis of chiral alkaloid monomers, liquid crystal compositions comprising the chiral alkaloid monomers, and polymerization of the liquid crystal compositions to provide polymer networks with useful cholesteric optical properties and stability.

This application claims the benefit of U.S. Provisional Application No.60/955,949, filed Aug. 15, 2007, which is by this reference incorporatedin its entirety as a part hereof for all purposes.

TECHNICAL FIELD

This invention is related to the chemical synthesis of chiral alkaloidmonomers, liquid crystal compositions comprising the chiral alkaloidmonomers, and polymerization of the liquid crystal compositions toprovide polymer networks with useful cholesteric optical properties andstability.

BACKGROUND

Thermotropic liquid crystals are generally crystalline compounds withsignificant anisotropy in shape. That is, at the molecular level, theyare characterized by a rod-like or disc like structure. When heated theytypically melt in a stepwise manner, exhibiting one or more thermaltransitions from a crystal to a final isotropic phase. The intermediatephases, known as mesophases, can include several types of smectic phaseswherein the molecules are generally confined to layers; and a nematicphase wherein the molecules are aligned parallel to one another with nolong range positional order. The liquid crystal phase can be achieved ina heating cycle, or can be arrived at in cooling from an isotropicphase. A comprehensive description of the structure of liquid crystalsin general, and twisted nematic liquid crystals in particular, is givenin “The Physics of Liquid Crystals,” P. G. de Gennes and J. Prost,Oxford University Press, 1995.

An important variant of the nematic phase is one wherein a chiral moietyis present therein, referred to as a twisted nematic, chiral nematic, orcholesteric phase. In this case, the molecules are parallel to eachother as in the nematic phase, but the director of molecules (theaverage direction of the rodlike molecules) changes direction throughthe thickness of a layer to provide a helical packing of the nematicmolecules. The pitch of the helix is perpendicular to the long axes ofthe molecules. This helical packing of anisotropic molecules leads toimportant and characteristic optical properties of twisted nematicphases including circular dichroism, a high degree of rotary power; andthe selective reflection of light, including ultraviolet, visible, andnear-IR light. Reflection in the visible region leads to brilliantlycolored layers. The sense of the helix can either be right-handed orleft-handed, and the rotational sense is an important characteristic ofthe material. The chiral moiety either may be present in the liquidcrystalline molecule itself, for instance, as in a cholesteryl ester, orcan be added to the nematic phase as a dopant, leading to induction ofthe cholesteric phase. This phenomenon is well documented, as discussedfor example in H. Bassler and M. M. Labes, J. Chem. Phys., 52, 631(1970).

There has been significant effort invested in methods for preparing, bysynthesis, polymerization and otherwise, stable polymer layersexhibiting fixed cholesteric optical properties. One approach has beento synthesize monofunctional and/or polyfunctional reactive monomersthat exhibit a cholesteric phase upon melting, formulate a low meltingliquid crystal composition, and polymerize the liquid crystalcomposition in its cholesteric phase to provide a polymer networkexhibiting stable optical properties of the cholesteric phase. Use ofcholesteric monomers alone, as disclosed in U.S. Pat. No. 4,637,896,provided cholesteric layers with the desired optical properties, but thepolymer layers possessed relatively weak mechanical properties.

Many efforts have been made to improve the physical properties andthermal stabilities by formulating twisted nematic monomer phases thatare capable of crosslinking polymerizations to provide polymer networks.A need remains, however, for polymerizable chiral monomers that havegood phase compatibility in polymerizable nematic liquid crystals andhigh helical twisting power (HTP). High HTP allows the use of smalleramounts of the expensive chiral component to be used in twisted nematicformulations to induce a desired pitch. Good phase compatibility isrequired to prevent premature crystallization or phase separation of thechiral monomers from the twisted nematic formulation.

Crosslinking chiral monomers with high HTP and good phase compatibility,based on the isosorbide chiral group, are disclosed in U.S. Pat. No.6,723,395. Chiral monomers with high HTP and good phase compatibility,based on alkaloid monomers are disclosed in U.S. Pat. No. 7,022,259.However, the latter chiral dopants are not capable of beingsubstantially covalently bonded to a polymer network. In someapplications these nonpolymerizable monomers may exhibit adequatestability. However, for many optical applications, the cholesteric layeris in contact with another layer. The other layer may be anothercholesteric layer or a different material. In this case, stability ofthe chiral dopant toward migration and/or extraction becomes asignificant issue. This is because, as discussed above, theconcentration and HTP of the chiral dopant significantly determines thepitch and thus the wavelength of maximum reflection. Thus, a needremains for chiral monomers that have good phase compatibility withpolymerizable nematic phases, exhibit high HTP, and exhibit significantstability in polymer networks toward migration.

SUMMARY

One embodiment of the inventions disclosed herein is a compound asrepresented by the structure of the following formula (I):D-S₁—(B—S₂)_(m)-(A₁S₃)_(n)—R_(p)  (I)wherein

D is a chiral moiety (D1) or (D2) derived, by formal removal of ahydroxyl group, from the alkaloids selected from the group consisting of(−) cinchonidine, CAS [485-71-2]; (+)-cinchonine, CAS [118-10-5];quinine, CAS [130-95-0] and quinidine, CAS [56-54-2]; and theirdihydro-derivatives:

X is hydrogen or —OCH₃;

R is —CH═CH₂ or —CH₂CH₃;

S₁ is a linking group selected from the group consisting of —O—,—OC(O)—, —OC(O)NH— and —OC(O)O—;

S₂ and S₃ are linking groups each independently selected from the groupconsisting of covalent bond, —O—, —S—, —C(O)—, —OC(O)—, —C(O)O—,—OC(O)O—, —OC(O)NR₁—, —NR₁C(O)O—, —SC(O)—, and —C(O)S—;

R₁ is hydrogen or C₁ to C₄ alkyl;

each B is a divalent radical independently selected from the groupconsisting of aliphatic and aromatic carbocyclic and heterocyclic groupshaving 1 to 16 carbon atoms; optionally having one or more fused ringsand optionally mono- or polysubstituted with L;

L is selected from the group consisting of the substitutents F, Cl, —CN,and —NO₂; and alkyl, alkoxy, alkylcarbonyl, and alkoxycarbonyl groups,having 1 to 8 carbon atoms, wherein one or more of the carbon atoms areoptionally substituted with F or Cl;

A₁ is a divalent linear or branched alkyl having 2 to 20 carbon atoms,optionally interrupted by linking groups selected from the group —O—,—S—, —C(O)—, —OC(O)— and —C(O)O—;

R_(p) is a polymerizable group;

m is an integer of 1 or 2; and

n is an integer of 0 or 1.

Another embodiment of the inventions hereof is a polymerizable liquidcrystal composition comprising at least one chiral compound of formula(I) as defined above. A further embodiment is a polymer network derivedfrom polymerization of the liquid crystal composition comprising atleast one compound of formula (I) as defined above; and morespecifically, a polymer network that exhibits significant stabilitytoward migration of the chiral compound. Another embodiment is anoptical element comprising the polymer network defined above.

The terms (meth)acrylate salt, (meth)acrylate ester, (meth)acrylateacid, and the like, herein encompass materials and the moietiescomprising the radical CH₂═C(R₂)—C(O)—O—; including methacrylate,wherein R₂ is methyl; acrylate, wherein R₂ is hydrogen; chloroacrylate,wherein R₂ is Cl; and fluoroacrylate, wherein R₂ is F; unlessspecifically defined otherwise.

DETAILED DESCRIPTION

The ability of a twisted nematic phase, which is also referred to hereinas a cholesteric phase or a chiral nematic phase, to selectively reflectlight in the infrared, visible or ultraviolet region is useful in manyapplications. When the propagation direction of plane polarized orunpolarized light is along the helical axis of the twisted nematiclayer, the wavelength of maximum reflection, λ₀, is governed by theequation λ₀=n_(a) p, wherein n_(a) is the average of n_(o) and n_(e),and n_(o) and n_(e) are defined as the ordinary and extraordinaryrefractive indices, respectively, of the twisted nematic phase measuredin the propagation direction; and wherein p is the pitch of the helix(the distance the helix takes to repeat itself). Light outside thevicinity of λ₀ is essentially unaffected in transmission. For light witha wavelength in the vicinity of wavelength λ₀, the twisted nematic phaseexhibits selective reflection of the light such that approximately 50%of the light is reflected and approximately 50% of the light istransmitted, with both the reflected and transmitted beams beingsubstantially circularly polarized. The pitch p can be tuned effectivelyby manipulating the amount of chiral dopant, the twisting power of thedopant and selection of the nematic materials. The pitch is sensitive totemperature, unwinding or tightening with a change in temperature; toelectric fields, dopants, and other environmental considerations. Thus,in the twisted nematic phase, manipulation of the pitch, and thus thewavelength of maximum reflection, can be accomplished with a widevariety of tools.

Depending upon the intrinsic rotatory sense of the helical nature of thetwisted nematic substance, i.e. whether it is right-handed orleft-handed, the light that is transmitted is either right-handcircularly polarized light (RHCPL) or left-hand circularly polarizedlight (LHCPL). In order to conform to popular convention, the twistednematic liquid crystal substances will be hereinbelow identified by thekind of light that is reflected in the wavelength region around λ₀. Whena cholesteric or twisted nematic layer is said to be right-handed it ismeant that it reflects RHCPL, and when a layer is said to be left-handedit is meant that it reflects LHCPL. A right-handed twisted nematicliquid crystal layer transmits LHCPL essentially completely, whereas thesame layer reflects RHCPL almost completely, at λ₀. This assumes, ofcourse, the cholesteric or twisted nematic layer is optimally aligned ina planar orientation. Conversely a left-handed twisted nematic liquidcrystal layer transmits RHCPL essentially completely, whereas the samelayer reflects LHCPL almost completely, at λ₀. Since plane polarized orunpolarized light contains equal amounts of RHCPL and LHCPL, a twistednematic layer is approximately 50 percent transmitting at λ₀ for theselight sources. This assumes, of course, the cholesteric or twistednematic layer is optimally aligned in a planar orientation.

In certain optical applications, e.g. solar control applications, it ispreferred that substantially all the light at some wavelengths bereflected. This requires at least one layer of each handedness, i.e. alayer reflecting RHCPL and a layer reflecting LHCPL, to be present. Onemethod for reflecting substantially all of the light in the vicinity ofλ₀ is to use two twisted nematic layers with similar λ₀, oneright-handed and one left-handed. Light in the region around λ₀transmitted by the first layer will be reflected by the second layer,with the result that substantially all of the incident light with awavelength in the vicinity of λ₀ will be reflected. In theory, this maybe accomplished by using enantiomeric chiral dopants of oppositechirality in matched twisted nematic layers. However, in most cases, oneor both chiral dopants of the pair are usually very expensive, orunavailable. Thus, it is necessary to seek out suitable chiral dopantsthat have good compatibility with nematic phases, have high HTP, may beused for the formation of right-handed nematic layers and left-handednematic layers, and exhibit excellent stability within polymer networks.The latter property is noteworthy because, as discussed above, theconcentration of chiral dopant largely determines magnitude of the pitchof the network.

One embodiment of the inventions disclosed herein is a compound asrepresented by the structure of the following formula (I):D-S₁—(B—S₂)_(m)-(A₁S₃)_(n)—R_(p)  (I)wherein

D is a chiral moiety (D1) or (D2) derived, by formal removal of ahydroxyl group, from the alkaloids selected from the group consisting of(−) cinchonidine, CAS [485-71-2]; (+)-cinchonine, CAS [118-10-5];quinine, CAS [130-95-0] and quinidine, CAS [56-54-2]; and theirdihydro-derivatives:

X is hydrogen or —OCH₃;

R is —CH═CH₂ or —CH₂CH₃;

S₁ is a linking group selected from the group consisting of —O—,—OC(O)—, —OC(O)NH— and —OC(O)O—;

S₂ and S₃ are linking groups each independently selected from the groupconsisting of covalent bond, —O—, —S—, —C(O)—, —OC(O)—, —C(O)O—,—OC(O)O—, —OC(O)NR₁—, —NR₁C(O)O—, —SC(O)—, and —C(O)S—;

R₁ is hydrogen or C₁ to C₄ alkyl;

each B is a divalent radical independently selected from the groupconsisting of aliphatic and aromatic carbocyclic and heterocyclic groupshaving 1 to 16 carbon atoms; optionally having one or more fused ringsand optionally mono- or polysubstituted with L;

L is selected from the group consisting of the substitutents F, Cl, —CN,and —NO₂; and alkyl, alkoxy, alkylcarbonyl, and alkoxycarbonyl groups,having 1 to 8 carbon atoms, wherein one or more of the carbon atoms areoptionally substituted with F or Cl;

A₁ is a divalent linear or branched alkyl having 2 to 20 carbon atoms,optionally interrupted by linking groups selected from the group —O—,—S—, —C(O)—, —OC(O)— and —C(O)O—;

R_(p) is a polymerizable group;

m is an integer of 1 or 2; and

n is an integer of 0 or 1.

In formula (I), the left side of the formula listed for S₁ is connectedto the chiral moiety (Ia) or (Ib). In a preferred embodiment S₁ is—OC(O)—. The term “optionally interrupted by linking groups selectedfrom the group —O—, —S—, —C(O)—, —OC(O)— or —C(O)O—” means that A₁includes alkyl radicals that have one or more of said linking groups,and if present, preferably have 1 to 3 said linking groups; providedthat only one linking group, including linking groups S₂ and S₃, isbonded to any one alkyl carbon atom, and there are no linking groupsbonded to each other. Examples of a suitable A₁ divalent radical thatcontain one or more linking groups are polyoxyalkylene chains, of theformula —(CH₂CH₂O)_(t)CH₂CH₂— wherein t is an integer of 1 to 9.

In one embodiment, —R_(p) is selected from the group consisting ofCH₂═C(R₂)—, glycidyl ether, propenyl ether, oxetane, and 1,2-, 1,3-, and1,4-substituted styryl and alkyl substituted styryl radicals, wherein R₂is hydrogen, Cl, F, CN, or CH₃. Preferably —R_(p) is CH₂═C(R₂)—, and R₂is hydrogen or CH₃. A preferred embodiment is wherein n=0, the radical—S₂—R_(p) is CH₂═C(R₂)—C(O)—O—, and R₂ is hydrogen or —CH₃. Anotherpreferred embodiment is wherein n=1, the radical —S₃—R_(p) isCH₂═C(R₂)—C(O)—O—, and R₂ is hydrogen or —CH₃. Another preferredembodiment is wherein S₁ is —O— or —OC(O)—. Another preferred embodimentis wherein S₁ and S₂ are —OC(O)—. In another preferred embodiment, whenS₂ is a linking group —OC(O)— or —SC(O)—, A₁ is a linear chain having 3to 20 carbon atoms.

The term “each B is a divalent radical independently selected from thegroup” means that when m=2, the two B units are selected independently,that is they may be the same or different. Preferably B is selected fromthe group consisting of:

wherein X₂ is a divalent radical selected from the group: —O—,—(CH₃)₂C—, and —(CF₃)₂C—; and L is as defined above.

In a preferred embodiment, each B is independently a divalent radicalselected from the group consisting of 1,4-cyclohexyl; 2,6-naphthyl;4,4′-biphenyl; and R₁₁-substituted-1,4-phenyl, wherein R₁₁ is H, —CH₃ or—OCH₃. The term “R₁₁-substituted-1,4-phenyl” refers to the radical

wherein R₁₁ can be bonded to any one of the four available carbon atoms.An especially preferred embodiment is wherein each B is independentlythe divalent radical R₁₁-substituted-1,4-phenyl.

Another embodiment is a class of compounds wherein, referring to formula(I), S₁ and S₂ are each —OC(O)—; m is an integer of 1; B is 2,6-naphthylor R₁₁-substituted-1,4-phenyl; and —R_(p) is CH₂═C(R₂)—. Compounds ofthis preferred group are selected from the group consisting of formulas(IIa), (IIb), (IIc) and (IId):

wherein D1, D2, R₁₁, and R₂ are as defined above.

Compounds of formula (IIa) can be made by the synthesis pathway outlinedin Scheme 1, which exemplifies the synthesis starting with quinine, CAS[130-95-0], (which is D1-OH) wherein within D1-OH, X is —OCH₃, and R is—CH═CH₂:

Quinine is esterified with a 4-tetrahydropyranyl benzoic acid of formula(IIa-1) in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimidehydrochloride (EDC); followed by cleavage of the tetrahydropyranyl (THP)ether with acid to provide a 4-hydroxybenzoate ester of formula (IIa-2).The 4-hydroxybenzoate ester (IIa-2) is acylated with (meth)acryloylchloride to provide (IIa).

Compounds of formula (IIc) can be made by acylation of quinine with6-(acryloyloxy)-2-naphthalenecarboxylic acid chloride, as illustrated inthe examples herein.

Herein, all synthetic paths are exemplified with quinine However,similar synthetic pathways can be used as well with: cinchonidine, CAS[485-71-2], which is D1-OH wherein X is hydrogen; cinchonine, CAS[118-10-5], which is D2-OH wherein X is hydrogen; quinidine CAS[56-54-2]; which is D2-OH wherein X is —OCH₃; and their correspondingdihydro derivatives wherein R is —CH₂CH₃. Thus, specific compoundswithin the classes of formula (IIa), (IIb), (IIIa), (IIIb), (IVa) and(IVb) are available using similar synthetic methods.

Another embodiment hereof is a class of compounds wherein, referring toformula (I), S₁ and S₂ are each —OC(O)—; m is an integer of 1; B is4,4′-biphenyl; and —R_(p) is CH₂═C(R₂)—. Compounds of this preferredclass are represented by formula is formula (IIIa) and (IIIb):

wherein D1, D2, and R₂ are as defined above.

Compounds of formula (IIa) can be made by the synthesis pathway outlinedin Scheme 2:

Another embodiment is a class of compounds wherein, referring to formula(I), S₁ S₂ and S₃ are each —OC(O)—; m is an integer of 2; each B isR₁₁-substituted-1,4-phenyl; and —R_(p) is CH₂═C(R₂)—. Compounds of thispreferred class are represented by formula (IVa) and (IVb):

wherein D1, D2, R₁₁, R₂, and A₁ are as defined above.

Compounds of formula (IVa) can be made by the synthesis pathway outlinedin Scheme 3:

The 4-hydroxybenzoate ester of formula (IIa-2) is acylated with the acidchloride (IVa-1), typically in the presence of an organic base such as atertiary amine.

Compounds of formula (I) are useful in polymerizable liquid crystalcompositions, also of the invention. Compounds of formula (I) are usefulas chiral dopants to induce chirality of a nematic phase to provide atwisted nematic phase. Useful twisted nematic phases can be provided bymixing the chiral dopants at about 0.5 to about 30 wt % based on thetotal nematic mixture. Preferred embodiments are polymerizable liquidcrystal compositions comprising at least one compound of formula (IIa),(IIb), (IIc), (IId), (IIIa), (IIIb), (IVa), and (IVb).

A wide variety of polymerizable and nonpolymerizable liquid crystals canbe used in the polymerizable liquid crystal compositions of theinvention including in those disclosed in Makromol. Chem. 190, 2255-2268(1989); Macromolecules, 1988, 31, 5940; Makromol. Chem. 192, 59-74(1991); J. Polym. Sci.: Part A: Polym. Chem., Vol. 37, 3929-3935 (1999);and Makromol. Chem. 190, 3201-3215 (1989). Additional polymerizablemonomers useful in liquid crystal compositions are disclosed in U.S.Pat. No. 5,833,880, DE 4408170, EP 261712, EP 331233 B1, EP 397263 B1,and WO1998047979, each of which is incorporated as a part hereof byreference. A preferred group of polymerizable monomers for thepolymerizable liquid crystal compositions of the invention are those offormula (VII):

wherein

R₂ is independently selected from the group: H, F, Cl, and CH₃;

n1 and n2 are, independently, integers 3 to 20;

u and v are, independently, integers 0, 1 or 2;

A is a divalent radical selected from the group:

wherein

R₃-R₁₀ are independently selected from the group: H, C₁-C₈ straight orbranched chain alkyl, C₁-C₈ straight or branched chain alkyloxy, F, Cl,phenyl, —C(O)CH₃, CN, and CF₃;

X₂ is a divalent radical selected from the group: —O—, —(CH₃)₂C—, and—(CF₃)₂C—; and

each B₃ and B₄ is a divalent radical independently selected from thegroup: 2,6-naphthyl; 4,4′-biphenyl; and R₁₁-substituted-1,4-phenyl,wherein R₁₁ is H, —CH₃ or —OCH₃;

with the proviso that when the sum of u+v is equal to 3 or 4, at leasttwo of B₃ and B₄ are R₁₁-substituted-1,4-phenyl.

A preferred embodiment is a polymerizable liquid crystal composition ofthe invention comprising polymerizable monomers wherein, referring toformula (VII), u is 1 and v is 0, and formula (VII) is formula (VIIIa):

wherein R₂ is independently H or CH₃; R₃-R₆ are independently H or —CH₃;n1 and n2 are independently integers of 3 to 20; and B₃ isR₁₁-substituted-1,4-phenyl, wherein R₁₁ is H, —CH₃ or —OCH₃.

Another preferred embodiment is a polymerizable liquid crystalcomposition of the invention comprising polymerizable monomers wherein,referring to formula (VII), u and v are 1, and formula (VII) is formula(IXa):

wherein R₂ is independently H or CH₃; R₃-R₆ are independently H or —CH₃;n1 and n2 are independently integers of 3 to 20; and B₃ and B₄ areR₁₁-substituted-1,4-phenyl, wherein R₁₁ is H, —CH₃ or —OCH₃.

Another preferred embodiment is a polymerizable liquid crystalcomposition of the invention comprising a mixture of polymerizablemonomers of formula (VIIIa) and (IXa).

The synthesis of compounds of formula (VII), (Villa) and (IXa), andliquid crystal mixtures thereof, is disclosed in pending U.S.application Ser. No. 11/731,289, which is incorporated in its entiretyas a part hereof for all purposes. The synthesis of Compounds 25, 26 and27, disclosed below, are specific examples of monomers of formula (IXa)and (VIIIa) that are used in the examples illustrating the preparationof polymerizable liquid crystal compositions. Preferred polymerizableliquid crystal compositions of the invention have a twisted nematicphase below 120° C.

The liquid crystal compositions of the invention are useful in preparingpolymer networks that exhibit the fixed optical properties of twistednematic polymer networks. The polymer network of the invention is one ormore polymerized layer(s) comprising a liquid crystal composition thatinclude: polymerized films, coatings, castings and prints; includingpatterned, unpatterned, variable and nonvariable optical properties;that can be made by a wide variety of methods as disclosed, forinstance, in U.S. Pat. Nos. 4,637,896, 6,010,643 and 6,410,130.

In particular, one preferred method for making a polymer networkcomprises involves providing a polymerizable twisted nematic mixture, inthe form of a twisted nematic or isotropic phase, with a polymerizationinitiator, preferably a radical initiator; applying the twisted nematicmixture to one or more substrates, where the substrate(s) optionallycontains an alignment layer, to provide a layer of the twisted nematicmixture; optionally treating the layer to provide a desired twistednematic phase; and polymerizing the twisted nematic phase, preferably byexposing the twisted nematic phase to actinic radiation.

The liquid crystal compositions of various embodiments of the inventioncan include a radical initiator, and preferably the radical initiator isa photoinitiator useful in conducting photochemical polymerizations. Forcuring by electron beams, such initiators are not required. Examples ofsuitable photoinitiators are isobutyl benzoin ether,2,4,6-trimethylbenzoyldiphenylphosphine oxide, 1-hydroxycyclohexylphenyl ketone,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)furan-1-one, mixtures ofbenzophenone and 1-hydroxycyclohexyl phenyl ketone,2,2-dimethoxy-2-phenylacetophenone, perfluorinated diphenyltitanocenes,2-methyl-1-(4-[methylthio]phenyl)-2-(4-morpholinyl)-1-propanone,2-hydroxy-2-methyl-1-phenylpropan-1-one, 4-(2-hydroxyethoxy)phenyl2-hydroxy-2-propyl ketone, 2,2-diethoxyacetophenone,4-benzoyl-4′-methyldiphenyl sulfide, ethyl 4-(dimethylamino)benzoate,mixtures of 2-isopropylthioxanthone and 4-isopropylthioxanthone,2-(dimethylamino)ethyl benzoate, d,1-camphorquinone,ethyl-d,1-camphorquinone, mixtures of benzophenone and4-methylbenzophenone, benzophenone, 4,4′-bisdimethylaminobenzophenone,triphenylsulfonium hexafluorophosphate or mixtures of triphenylsulfoniumsalts. Preferably the photoinitiators are present at a level of about0.1 wt % to 3 wt % of the polymerizable liquid crystal mixture.

As a substrate, for example, a glass or quartz sheet, as well as aplastic film or sheet can be used. It is also possible to put a secondsubstrate on top of the coated mixture prior to, during and/or afterpolymerization. The substrates can optionally be removed afterpolymerization. When using two substrates in the case of curing byactinic radiation, at least one substrate has to be transmissive for thepolymerization. Isotropic or birefringent substrates can be used. Incase the substrate is not removed from the polymerized film afterpolymerization, preferably isotropic substrates are used.

Preferably at least one substrate is a plastic substrate, for example, afilm of polyester such as polyethylene terephthalate (PET), ofpolyvinylalcohol (PVA), polycarbonate (PC) or triacetylcellulose (TAC),especially preferably a PET film or a TAC film. As a birefringentsubstrate, for example, an uniaxially stretched plastic film can beused. Preferably the substrates are buffed with a buffing cloth toenhance alignment of the chiral nematic phase.

Applying the twisted nematic mixture can be accomplished by any methodthat gives a uniform layer, or if desired, a patterned or non-uniformlayer. Coating, including rod-coating, extrusion coating, gravurecoating, slot-die coating and spin-coating, spraying, printing, blading,knifing, or a combination of methods, can be used.

Preferably the polymerizable liquid crystal mixture is coated as a thinlayer on a substrate or between substrates, and aligned in its chiralmesophase into planar orientation, wherein the axis of the molecularhelix extends transversely to the layer. Planar orientation can beachieved, for example, by shearing the mixture, e.g., by means of adoctor blade. It is also possible to put a second substrate on top ofthe coated material. In this case, the shearing caused by puttingtogether the two substrates is sufficient to give good alignment.Alternatively it is possible to apply an alignment layer, for example alayer of rubbed polyimide or sputtered SiO₂, on top of at least one ofthe substrates, or to apply an electric or magnetic field to the coatedmixture, in order to induce or enhance planar alignment. Usefulpolyimide alignment layers are disclosed in U.S. Pat. No. 6,887,455.Alignment of twisted nematic phases by coating of dilute liquid crystalmixtures is disclosed in U.S. Pat. No. 6,410,130. Planar alignment maybe induced or enhanced by addition of one or more surface-activecompounds to the polymerizable mixture.

Treating the liquid crystal layer to provide a desired liquid crystalphase can include, cooling or heating the liquid crystal layer, forinstance to achieve a desired phase or optical property; application ofa mechanical shear to the liquid crystal layer, for instance, byapplication of a knife blade to the liquid crystal layer, shearing twoor more substrates wherein the liquid crystal layer is interposed, orvibration, sonication or other form of agitation to the substrate(s).

Another preferred method for making a polymer network involves providingan isotropic solution that contains a polymerizable liquid crystalmixture, a polymerization initiator, preferably a photoinitiator, and acarrier solvent; applying the isotropic solution to one or moresubstrate(s), preferably where the substrate(s) contains an alignmentlayer, to provide an isotropic layer; removing the carrier solvent and,optionally, treating the layer, to provide a desired liquid crystalphase; and polymerizing the liquid crystal phase, preferably by exposingthe liquid crystal phase to actinic radiation. U.S. Pat. Nos. 6,010,643and 4,637,896 exemplify preparation of a liquid crystal layer using twosubstrates to form a cell. U.S. Pat. Nos. 4,637,896 and 6,410,130exemplify preparation of a liquid crystal layer from an isotropicsolution, followed by polymerization.

Wherein a carrier solvent is used with the liquid crystal composition,coating and spraying are preferred methods for applying the isotropicsolution. Removing the carrier solvent can be accomplished by allowingthe carrier solvent to evaporate, with or without heating and/orapplication of a vacuum. Allowing the carrier solvent to evaporate alsomay be accompanied and/or followed by application of a mechanical shearto the liquid crystal layer as described above. Examples of carriersolvents are linear or branched esters, especially acetic esters, cyclicethers and esters, alcohols, lactones, aliphatic and aromatichydrocarbons, such as toluene, xylene and cyclohexane, chlorinatedhydrocarbons, such as dichloromethane, 1,1,2,2-tetrachloroethane, andalso ketones, amides, N-alkylpyrrolidones, especiallyN-methylpyrrolidone. Additional examples of useful solvents includetetrahydrofuran (THF), dioxane, methyl ethyl ketone (MEK), and propyleneglycol monomethyl ether acetate.

The liquid crystal compositions of the invention may further comprisesmall amounts of a polymerizable diluent including, for example,2-ethoxyethyl acrylate, diethylene glycol diacrylate, ethylene glycoldimethacrylate, diethylene glycol dimethacrylate, triethylene glycoldimethacrylate, diethylene glycol monomethyl ether acrylate,phenoxyethyl acrylate, tetraethylene glycol dimethacrylate,pentaerythritol tetraacrylate and ethoxylated pentaerythritoltetraacrylate.

The liquid crystal compositions of the invention may further comprisesmall amounts of surfactants, leveling agents, viscosity modifiers,wetting agents, defoamers, and UV and radical stabilizers. Selectionwill often be based upon observed coating and alignment quality and thedesired adhesion of the final polymer network to the substrate and otherlayers. Typical surfactants comprise siloxy-, fluoryl-, alkyl- andalkynyl-substituted surfactants. These include surfactants sold underthe trade names BYK (Byk Chemie, Wesel, Germany), ZONYL (DuPont), TRITON(Dow Chemical Co., Midland, Mich.), SURFUNOL and DYNOL (Air Products,Inc. Allentown, Pa.). A stabilizer may be used to prevent undesiredspontaneous polymerization, for example, during storage of thecomposition. A wide variety of stabilizers may be used for this purpose.Typical examples for stabilizers are 4-ethoxyphenol, 4-methoxyphenol,methyl hydroquinone, and butylated hydroxytoluene (BHT).

Exposing the liquid crystal phase to actinic radiation can be done by avariety of means, including heat, microwave radiation, UV and visiblelight, and electron beam and other radiation. Radiation sources caninclude Hg arc lamps, Xenon lamps, laser light sources, and the like.The exposing can be done selectively, if so desired, and may include theuse of a mask, or a computer controlled scan system. A detaileddescription of the in situ polymerization of polymerizable mesogeniccompounds can be found, for example, in D. J. Broer et al.,Makromolekulare Chemie 190, 2255 (1989).

Polymerization is preferably carried out under an atmosphere of inertgas, preferably under a nitrogen atmosphere. The polymerization can beconducted at room temperature, below room temperature or above roomtemperature if so desired. The optical properties of a twisted nematicliquid crystal phase, particularly the wavelength of reflection, can betuned, to some extent, by adjusting the temperature of the phase. In apreferred embodiment, the polymerization is conducted above roomtemperature (˜25° C.), preferably about 40° C. to about 10° C. below theisotropic point of the liquid crystal composition. A preferredtemperature range for conducting the polymerization is about 50° C. toabout 90° C., provided this is below the isotropic point of the liquidcrystal composition. The polymerization above room temperature generallyprovides a polymer network with a lower haze, as determined by visualobservation, than one provided by polymerization at room temperature.

The polymer networks of the invention can be made either flexible orbrittle depending on crosslinking The brittle films can be flaked andthe flakes used as pigments in a variety of inks or paints for use incosmetics and automobile paint. The films can be combined with otherpigments or pigment layers, for instance black layers, that act toenhance the brilliance of the reflected light.

The polymer networks of the invention exhibit more stable opticalproperties than polymer networks having chiral dopants that are notcovalently linked to the network. The differences in stability arereadily apparent when polymer networks are overcoated with second orthird layer of polymerizable liquid crystal composition, referred to as“overcoating”, which is a useful process in fabrication of multilayeroptical devices, having multiple wavelengths of maximum reflection. Theoptical properties, specifically the wavelength of maximum reflectionremain substantially intact, when the polymer networks of the inventionare overcoated with a second solution comprising liquid crystalmonomers; whereas the optical properties of polymer networks wherein thechiral dopant is not covalently bonded to the network experience asignificant shift in wavelength of maximum reflection under similarcircumstances. Furthermore, polymer networks wherein the chiral dopantis not covalently bonded to the network appear to act as sources ofchiral contaminates when overcoated with a second solution comprisingliquid crystal monomers. As a result the second layer tends to exhibit asubstantial shift in wavelength of maximum reflection to lowerwavelength (tighter pitch). This affect could be explained if chiraldopant were being extracted into the second layer. On the contrary,coating a second layer of polymerizable liquid crystal monomers onto apolymer network of the invention, wherein the chiral dopants aresubstantially covalently bonded to the network, shows no evidence ofextraction of the chiral dopant into the second layer. This is evidencedby the fact that the wavelength of maximum reflection of the secondlayer is substantially identical to that of the same polymerizableliquid crystal composition coated as a single layer. The inventionshereof are not, however, limited to any particular theory of operation.

The polymer networks of the invention are useful as optical elements orcomponents of an optical element. An optical element is any film,coating or shaped object that is used to modify the characteristics oflight. The modifications produced by optical elements include changes inthe intensity of light through changes in transmission or reflectivity,changes in wavelength or wavelength distribution, changes in the stateof polarization, changes in the direction of propagation of part or allof the light, or changes in the spatial distribution of intensity by,for example, focusing, collimating, or diffusing the light. Examples ofoptical elements include linear polarizers, circular polarizers, lenses,mirrors, collimators, diffusers, reflectors and the like. One specificexample of an optical element is a layer of a cholesteric polymernetwork of the invention that reflects light within the vicinity of λ₀,employed in a window structure. One preferred embodiment of theinvention is a polymer network having a wavelength of maximum reflectionin the range of about 280 to about 2500 nm; and more preferably, in therange of about 700 to about 1400 nm.

EXAMPLES

This invention is further defined in the following examples. It shouldbe understood that these examples, while indicating preferredembodiments of the invention, are given by way of illustration only. Theselection of the embodiments set forth below to illustrate theinventions hereof does not indicate that materials, components,reactants, ingredients, conditions or designs not described in theseexamples are not suitable for practicing these inventions, or thatsubject matter not described in these examples is excluded from thescope of the appended claims and equivalents thereof.

In the examples, thermal transitions are given in degrees Centigrade.The following notations are used to describe the observed phases:K=crystal, N=nematic, S=smectic, TN*=twisted nematic, X=unidentifiedphase, I=isotropic, P=polymerized. The thermal transitions and phaseassignments were made with differential scanning calorimetry andhotstage optical microscopy. The following abbreviations are used in theexamples:

DCM=dichloromethane,

DMAc=dimethyl acetamide,

DMAP=4-dimethylamino pyridine,

DI water=deionized water,

EDC=1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride,

IPA=isopropyl alcohol,

mp=melting point,

pTSA=p-toluenesulfonic acid,

PPTS=pyridinium p-toluenesulfonate,

THF=tetrahydrofuran,

TEA=triethylamine,

THP=tetrahydropyranyl,

RT=room temperature.

For the examples, the following compounds were first prepared:

Compounds 25, 26 and 27 are liquid crystal monomers that were used informulation of liquid crystal mixtures of the various embodiments of theinvention. The syntheses of the monomers are disclosed in pending U.S.application Ser. No. 11/731,289, which is incorporated in its entiretyas a part hereof for all purposes, and are illustrated in the followingSchemes 5-7.

A mixture of 4-hydroxybenzoic acid (240.0 g), methylhydroquinone (100.2g), pTSA (6 g), and xylenes (1.5 L) was heated to reflux under anitrogen atmosphere for a total of 26 h in a flask equipped with aDean-Stark trap, condenser and mechanical stirrer. Additional pTSA (6.0g portions) was added after 8 and 18 h after cooling the reactionmixture RT. The final reaction mixture was cooled to RT, the solidscollected and washed with hexanes. The solids were slurried with hotacetone (600 mL) and cooled to RT, collected and dried to provideCompound 25A: ¹H NMR (DMSO-d₆, 500 MHz) δ 2.16 (s, 3H), 6.93 (d, J=8.8Hz, 2H), 6.95 (d, J=8.8 Hz, 2H), 7.13 (m, 1H), 7.23 (m, 2H), 7.99 (d,J=8.8 Hz, 2H), 8.02 (d, J=8.8 Hz, 2H), 10.51 (s, 2H).

A mixture of Compound 25A (100 g), THF (750 mL), and TEA (165 mL) wascooled to 0° C. A mixture of 6-bromohexanoyl chloride (126.0 g) in THF(400 mL) was added over about 0.75 h. The mixture was stirred at 0° C.for 2 h and allowed to warm to RT, and stirred for 2 h. The mixture waspoured into water (1.5 L) and hydrochloric acid (37%) was added untilthe mixture was pH 6. The mixture was stirred for 15 min and the solidscollected. The solids were rinsed with water, methanol and then dried toprovide Compound 25B: ¹H NMR (CDCl₃, 500 MHz) δ 1.60 (m, 4H), 1.81 (m,4H), 1.95 (m, 4H), 2.25 (s, 3H), 2.62 (t, J=7.4 Hz, 2H), 2.63 (t, J=7.4Hz, 2H), 3.45 (t, J=6.8 Hz, 4H), 7.10 (dd, J=8.6, 2.7 Hz, 1H), 7.14 (d,J=2.7, 1H), 7.19 (d, J=8.6 Hz, 1H), 7.24 (d, J=8.7 Hz, 2H), 7.25 (d,J=8.7 Hz, 2H), 8.22 (d, J=8.7 Hz, 2H), 8.25 (d, J=8.7 Hz, 2H).

To a mixture of Compound 25B (20.0 g), potassium bicarbonate (25.1 g),tetrabutyl ammonium iodide (5.14 g), 2,6-di-tert-butyl-4-methylphenol(1.04 g), and THF (350 mL) was added acrylic acid (5.73 mL). The mixturewas heated at 65° C. for 9 h and then allowed to stir at RT overnight.The mixture was partition between ethyl ether/water, and the ether layerwashed with several portions of water. The ether layer was dried and thesolvent removed and the product recrystallized from isopropanol toprovide Compound 25 (17.25 g): ¹H NMR (CDCl₃, 500 MHz) δ54 (m=4H), 1.77(m, 4H), 1.83 (m, 4H), 2.25 (s, 3H), 2.624 (t, J=7.4 Hz, 2H), 2.629 (t,J=7.4 Hz, 2H), 4.21 (t, J=6.6, 4H), 5.82 (dd, J=10.4, 1.3 Hz, 2H), 6.13(dd, J=17.3, 10.4 Hz, 2H), 6.40 (dd, J=17.3, 1.3 Hz, 2H), 7.10 (dd,J=8.7, 2.7 Hz, 1H), 7.15 (d, J=2.7, 1H), 7.19 (d, J=8.7, 1H), 7.24 (d,J=8.6 Hz, 2H), 7.25 (d, J=8.6 Hz, 2H), 8.22 (d, 8.6 Hz, 2H), 8.25 (d,J=8.6 Hz, 2H).

Using a similar procedure to that used for Compound 25B, Compound 25Awas acylated with 4-bromobutyroyl chloride to provide Compound 26A,followed by displacement of the bromides with acrylate to provideCompound 26: ¹H NMR (CDCl₃, 500 MHz) δ 2.17 (m, 4H), 2.26 (s, 3H), 2.73(t, J=7.3 Hz, 2H), 2.74 (t, J=7.3 Hz, 2H), 4.308 (t, J=6.2 Hz, 2H),4.310 (t, J=6.2 Hz, 2H), 5.858 (dd, J=10.5, 1.4 Hz, 1H), 5.860 (dd,J=10.5, 1.4 Hz, 1H), 6.144 (dd, J=17.4, 10.5 Hz, 1H), 6.146 (dd, J=17.4,10.5 Hz, 1H), 6.434 (dd, J=17.4, 1.4 Hz, 1H), 6.437 (dd, J=17.4, 1.4 Hz,1H), 7.10 (dd, J=8.6, 2.8 Hz, 1H), 7.15 (d, J=2.6, 1H), 7.19 (d, J=8.8Hz, 1H), 7.25 (d, J=8.8 Hz, 2H), 7.27 (d, J=8.8 Hz, 2H), 8.23 (d, J=8.8Hz, 2H), 8.26 (d, J=8.8 Hz, 2H).

A mixture of 4-hydroxybenzoic acid (80 g), hydroquinone (64 g), pTSA (2g), xylenes (500 mL) was heated to reflux in a flask equipped with aDean-Stark trap, condenser and mechanical stirrer until about 10 mL ofwater were collected. After cooling to room temperature the solids werefiltered off, washed with hexanes, and dried. The solids were placedinto 600 mL of boiling acetone and stirred for 30 min.

The mixture was filtered hot to eliminate traces of insoluble material.After cooling to RT, DI water (1500 mL) was added slowly to precipitatethe product. The precipitated product was filtered off and dried toprovide Compound 27A. ¹H NMR (CDCl₃, 500 MHz) δ 6.78 (d, 8.9 Hz, 2H),6.90 (d, J=8.8 Hz, 2H), 7.00 (d, J=8/9 Hz, 2H), 7.94 (d, J=8.8 Hz, 2H),9.42 (s, 1H), 10.44 (s, 1H).

Compound 27B was prepared using an analogous procedure as was describedabove for the synthesis of Compound 25B. ¹H NMR (CDCl₃, 500 MHz) δ1.59(m, 4H), 1.80 (m, 4H), 1.94 (m, 4H), 2.59 (t, J=7.4 Hz, 2H), 2.63 (t,J=7.4 Jz, 2H), 3.441 (t, J=6.7 Hz, 2H), 3.446 (t, J=6.7 Hz, 2H), 7.14(d, J=9.0 Hz, 2H), 7.22 (d, 9.0 Hz, 2H), 7.24 (d, 8.8 Hz, 2H), 8.22 (d,8.8 Hz, 2H).

Compound 27 was prepared using an analogous procedure as was describedabove for the synthesis of Compound 25. ¹H NMR (CDCl₃, 500 MHz) δ 1.52(m, 4H), 1.76 (m, 4H), 1.78 (m, 4H), 2.59 (t, J=7.4 Hz, 2H), 2.62 (t,J=7.4 Hz, 2H), 4.19 (t, J=6.6 Hz, 2H), 4.20 (t, J=6.6 Hz, 2H), 5.823(dd, 1H), 5.826 (dd, 1H), 6.122 (dd, 1H), 6.127 (dd, 1H), 6.404 (dd,1H), 6.407 (dd, 1H), 7.13 (d, J=8.6 Hz, 2H), 7.21 (d, J=8.6 Hz, 2H),7.23 (d, J=8.6 Hz, 2H), 8.21 (d, J=8.6 Hz, 2H).

Compound 28 was prepared in a similar manner as described for thesynthesis of Compound 2 by reacting acid chloride of4′-ethyloxy-4-biphenylcarboxylic acid with quinine Compound 28 had a mp76-78° C.; MS (APCI): m/z [M+H⁺] calcd for C₃₅H₃₇O₃N₂: 533.2804; found:533.2792. Compound 28 was used in the comparative example A todemonstrate the differences in performance between the polymerizablechiral dopants of the invention and nonpolymerizable chiral dopant knownart as disclosed in U.S. Pat. No. 7,022,259.

Example 1

This example illustrates the synthesis of the chiral dopant Compound 2

Compound 1 was first prepared. To a mixture of4′-hydroxy-4-biphenylcarboxylic acid (2.00 g), NaOH (1.16 g), dioxane(15 mL), and DI water (20 mL) under nitrogen was cooled down to 10° C.,was added acryloyl chloride (0.83 g) drop-wise. The mixture was allowedto stir at RT for 4 h. The mixture was acidified with 1 M HCl solutionand filtered. The isolated solid was washed with water-acetone (1:1 v/v)to provide Compound 1 (1.88 g): mp 247-250° C.

A mixture of Compound 1 (0.80 g), DMF (3 drops), and anhydrous THF (10mL), under nitrogen atmosphere, was cooled down to 0° C. A solutioncontaining THF (10 mL) and oxalyl chloride (0.38 mL) was addeddrop-wise. The solution mixture was stirred at 0° C. for 30 min and atRT for 4.5 h. The mixture was concentrated to provide the acid chlorideof Compound 1. A mixture of quinine (0.92 g), TEA (0.79 mL), DMAP (0.035g), and DCM (20 mL) under nitrogen was cooled to 0° C.; followed bydropwise addition of the acid chloride of Compound 1 in DCM (10 mL). Themixture was stirred at 0° C. for 30 min and at RT for 12 h. Water (75mL) was added and the mixture acidified with 0.5 M HCl. The mixture wasextracted with DCM and the combined organic layers were washed with 5 wt% aqueous Na₂CO₃, water, and dried over anhydrous MgSO₄. The solutionwas filtered and concentrated, and the crude material purified withsilica chromatography to provide Compound 2 (1.20 g): mp 78-81° C.; MS(APCI): m/z [M+H⁺] calcd for C₃₆H₃₅O₅N₂; 575.2546; found: 575.2536.

Example 2

This example illustrates the synthesis of Compound 4.

Compound 3 was first prepared. A mixture of 6-hydroxy-2-naphtholic acid(2.00 g), NaOH (0.85 g), dioxane (10 mL), DI water (20 mL) undernitrogen atmosphere was cooled down to 10° C. Acryloyl chloride (0.95 g)was added dropwise. The reaction mixture was allowed to stir at RT for 4h. The mixture was acidified with 1 M HCl solution, and filtered. Theisolated solid was washed with water-acetone mixture (1:1 v/v) toprovide Compound 3 (1.25 g): mp 210-212° C.

The acid chloride of Compound 3 was synthesized following a similarprocedure in the preparation of acid chloride of Compound 1. To amixture of (−)-cinchonindine (0.81 g), TEA (0.77 mL), DMAP (0.034 g),and DCM (20 mL), under nitrogen atmosphere and cooled down to 0° C., wasdropwise added the acid chloride of Compound 3 (0.76 g) in DCM (10 mL).The mixture was stirred at 0° C. for 30 min and at RT for 20 h. Water(75 mL) was added and the mixture was acidified with 0.5 M HCl. Themixture was extracted DCM and the combined organic layers were washedwith 5 wt % aqueous Na₂CO₃ and water, and dried over anhydrous MgSO₄,filtered, and concentrated. The crude product was purified with silicachromatography to provide Compound 4 (1.00 g): mp 70-72° C.; MS (APCI):m/z [M+H⁺] calcd for C₃₃H₃₁O₄N₂: 519.2284; found: 519.2292.

Example 3

This example illustrates the synthesis of Compound 5.

Compound 5 was synthesized following similar procedure in thepreparation of Compound 4. To a mixture of quinine (0.92 g), TEA (0.79mL), DMAP (0.035 g), and DCM (20 mL), under nitrogen atmosphere andcooled down to 0° C., was dropwise added acid chloride of Compound 3(0.76 g) in DCM (10 mL). The mixture was stirred at 0° C. for 30 min andat RT for 12 h. Water (75 mL) was added and the mixture was acidifiedwith 0.5 M HCl. The mixture was extracted with DCM and the combinedorganic layers were washed with 5 wt % aqueous Na₂CO₃ and water, driedover anhydrous MgSO₄, filtered, and concentrated. The crude product waspurified with silica chromatography to provide Compound 5 (1.00 g): mp70-72° C.; MS (APCI): m/z [M+H⁺] calcd for C₃₄H₃₃O₅N₂: 549.2389; found:549.2373.

Example 4

This Example illustrates the synthesis of Compound 9.

Compound 6 was first prepared. To a mixture of p-hydroxybenzoic acid(20.1 g), PPTS (0.12 g) in DCM (80 mL) was added 3,4-dihydro-2H-pyran(14.6 mL). The reaction mixture was allowed to stir at RT overnight. Thesolution mixture was filtered, washed with ethyl ether, and dried toprovide Compound 6 (19.0 g): ¹H NMR (CDCl₃, 500 MHz) δ 1.62 (m, 1H),1.70 (m, 2H), 1.89 (m, 2H), 2.01 (m, 1H), 3.63 (m, 1H), 3.86 (m, 1H),5.52 (t, J=3.1 Hz, 1H), 7.10 (m, 2H), 8.06 (m, 2H), 10.1 (br s, 1H).

To a mixture of quinine (5.57 g), Compound 6 (5.73 g), DMAP (2.10 g) inDCM (150 mL), under nitrogen, was added EDC (9.89 g) in DCM (15 mL). Themixture was allowed to stir at RT overnight. The solution mixture waswashed with water, 0.5 M HCl solution, 0.1 M NaOH solution, and water.The organic layer was dried with anhydrous MgSO₄, filtered andconcentrated to provide Compound 7 (7.35 g).

To a mixture of Compound 7 (6.09 g) in THF/methanol (1:1, 150 mL) wasadded HCl (37%, 1.25 mL). The mixture was heated to 50° C. for 10 hunder nitrogen atmosphere. The mixture was cooled to RT, neutralizedwith 5 wt.% aqueous Na₂CO₃, concentrated, and precipitated in water. Thesolid was further washed with water, filtered, and dried to provideCompound 8 (4.36 g): mp 215-217° C.

A mixture of Compound 8 (1.00 g) and TEA (0.94 mL) in THF (25 mL) wascooled to 0° C. A mixture of acryloyl chloride (0.27 mL) in THF (5 mL)was added dropwise. The reaction mixture was allowed to stir at 0° C.for 30 min and at RT for 4 h. The reaction mixture was filtered,acidified with 0.5 M HCl solution, extracted with DCM. The combinedorganic layer was washed with water, dried with anhydrous MgSO₄,filtered, and concentrated to provide Compound 9 (1.16 g): mp 55-57° C.;MS (APCI): m/z [M+H⁺] calcd for C₃₀H₃₁O₅N₂: 499.2233; found: 499.2229.

Example 5

This Example illustrates the synthesis of Compound 11.

Compound 10 was first made following the procedure reported inPCT/JP2005/004389. 6-Hydroxyhexanoic acid was synthesized by basehydrolysis of caprolactone. Caprolactone (100 g) was added to a mixtureof potassium hydroxide (145 g), methanol (110 mL), and THF (390 mL). Theresulting mixture was stirred at room temperature overnight. Thesolution was then acidified with HCl and extracted with ethyl acetate.The combined organic layers were washed with water, dried, filtered, andconcentrated to obtain 6-hydroxyhexanoic acid. ¹H NMR (CDCl₃, 500 MHz) δ1.44 (m, 2H), 1.60 (m, 2H), 1.68 (m, 2H), 2.37 (t, J=7.5 Hz, 2H), 3.66(t, J=6.5 Hz, 2H), 5.80 (br, 1H).

6-Hydroxyhexanoic acid was then converted to 6-acryloyloxyhexanoic acid.A mixture of 6-hydroxyhexanoic acid (10 g),2,6-di-tert-butyl-4-methylphenol (0.5 g), and DMAc (57 mL) was cooled to0° C. Acryloyl chloride (17.2 g) was then added dropwise. After stirringfor 3.5 h, pyridine (12 mL) and water (12 mL) were slowly added. Afterstirring for another 2 h, the solution was acidified with dilute HCl andextracted with ethyl acetate. The combined organic layer was washed withwater, dried, filtered, and concentrated to afford 6-acryloyloxyhexanoicacid. ¹H NMR (CDCl₃, 500 MHz) δ 1.46 (m, 2H), 1.70 (m, 4H), 2.37 (t,J=7.3 Hz, 2H), 4.17 (t, J=6.4 Hz, 2H), 5.82 (d, J=10.4 Hz, 1H), 6.12(dd, J=17.3, 10.5 Hz, 1H), 6.39 (d, J=17.3 Hz, 1H), 11.59 (br, 1H).

Compound 10 was obtained by esterification of 6-acryloyloxyhexanoic acidwith 4-hydroxybenzoic acid. To a mixture of 6-acryloyloxyhexanoic acid(5.0 g), THF (20 mL) and DMF (5 drops), cooled to 0° C., was addeddrop-wise a solution of oxalyl chloride (1.70 mL) in THF (25 mL). Afterstirring at 0° C. for 30 min and at RT for 4 h, solvent was removed toprovide the corresponding acid chloride that was re-dissolved in THF (20mL). To a mixture of 4-hydroxybenzoic acid (2.04 g), TEA (3.74 mL), DMAP(0.16 g) in THF (75 mL), cooled to 0° C., 6-acryloyloxyhexanoic acidchloride in THF (20 mL) was added dropwise. After stirring at 0° C. for20 min and at RT for 12 h, water was acidified with 0.1 M HCl solution,extracted with DCM, washed with water, dried with anhydrous MgSO₄,filtered, and concentrated. The crude mixture was purified by washingwith a mixture of isopropanol and hexane to provide Compound 10 (3.20g). ¹H NMR (CDCl₃, 500 MHz) δ 1.53 (m, 2H), 1.76 (m, 2H), 1.82 (m, 2H),2.61 (t, J=7.5 Hz, 2H), 4.20 (t, J=3.2 Hz, 2H), 5.82 (dd, J=10.5, 1.4Hz, 1H), 6.13 (dd, J=17.3, 10.4 Hz, 1H), 6.41 (dd, J=17.3 Hz, 1.5 Hz,1H), 7.20 (m, 2H), 8.14 (m, 2H).

To a mixture of Compound 10 (0.36 g), THF (20 mL), and DMF (3 drops),cooled to 0° C., was added drop-wise oxalyl chloride (0.23 mL) in THF(10 mL). After stirring at 0° C. for 30 min and at RT for 4 h, solventwas removed and the resulting acid chloride was dissolved in DCM (10 mL)and added to a mixture of Compound 8 (0.50 g), TEA (0.31 mL) and DCM (20mL), cooled to 0° C. After stirring at 0° C. for 30 min and at RT for 4h, the mixture was acidified with 0.1 M HCl solution and extracted withDCM. The combined organic layers were washed with water, dried withanhydrous MgSO₄, filtered, and concentrated. The crude product waspurified by silica chromatography to obtain Compound 11 (0.54 g): mp57-60° C.; MS (APCI): m/z [M+H⁺] calcd for C₄₃H₄₅O₉N₂: 733.3125; found:733.3104.

Example 6

This example illustrates the preparation of Mixture 1 and thepreparation of a liquid crystal polymer network.

Mixture 1:

Compound 2 (0.037 g), Compound 25 (0.157 g), Compound 26 (0.078 g),Compound 27 (0.059 g), and IRGACURE 184 photoinitiator (Ciba SpecialtyChemicals, Ardsley New York) (0.006 g) were combined and dissolved inDCM. The solution was filtered (0.45 micron filter), and the DCM wasremoved to provide Mixture 1: phase behavior: 1^(st) heating: X−43.6TN*66.2 I; 1^(st) cooling: I 80.8 TN*−33.3 X; 2^(nd) heating: X−46.1TN*85.1 I.

A polyethylene terephthalate film was hand rubbed with a YoshikawaYA-20-R rubbing cloth (Yoshikawa Chemical Company, Osaka, Japan).Mixture 1 was dissolved in xylenes to provide a 30 wt % solution. Thesolution was coated by hand using a Wire Size 20 Wire Wound Lab Rod(Paul N. Gardner Company, Pompano Beach, Fla.). The wet coating washeated at 60° C. for 5 min to allow solvent evaporation and alignment ofthe liquid crystal composition. The coated film was positioned 5.5 cmbelow a BLAK-RAY long wave UV mercury lamp (Model B-100 AP, UVP Inc.,Upland, Calif., with a power of 35 mW/cm²) and was exposed for 5 minunder a nitrogen atmosphere to provide a crosslinked polymer network.The crosslinked film exhibited a wavelength of reflection at 625 nm.

Example 7

Mixture 2:

Compound 4 (0.037 g), Compound 25 (0.157 g), Compound 26 (0.078 g),

Compound 27 (0.059 g), and IRGACURE 184 photoinitiator (0.006 g) werecombined and dissolved in DCM. The solution was filtered (0.45 micronfilter), and the solvent was removed to provide Mixture 2: phasebehavior: 1^(st) heating: X−46.0 TN*107.7 I; 1^(st) cooling: I 76.7TN*−27.5 X; 2^(nd) heating: X−26.9 TN*81.2 I. Coating and polymerizationof a film derived from Mixture 2 was performed following similarprocedures as described in Example 6 to provide a crosslinked polymernetwork: wavelength of reflection=1050 nm.

Example 8

Mixture 3:

Compound 5 (0.037 g), Compound 25 (0.157 g), Compound 26 (0.078 g),

Compound 27 (0.059 g), and IRGACURE 184 photoinitiator (0.006 g) werecombined and dissolved in DCM. The solution was filtered (0.45 micronfilter), and the solvent was removed to provide Mixture 3: phasebehavior: 1^(st) heating: X−50.7 TN*85.8 I; 1^(st) cooling: I 77.2TN*−26.7 X; 2^(nd) heating: X−27.9 TN*81.9 I. Coating and polymerizationof a film derived from Mixture 3 was performed following similarprocedures as described in Example 6 to provide a crosslinked polymernetwork: wavelength of reflection=979 nm.

Example 9

Mixture 4:

Compound 9 (0.037 g), Compound 25 (0.157 g), Compound 26 (0.078 g),

Compound 27 (0.059 g), and IRGACURE 184 photoinitiator (0.006 g) werecombined and dissolved in DCM. The solution was filtered (0.45 micronfilter), and the solvent was removed to provide Mixture 4: phasebehavior: 1^(st) heating: X−37.9 TN*62.1 I; 1^(st) cooling: I 74.2TN*−31.7 X; 2^(nd) heating: X−27.2 TN*77.7 I. Coating and polymerizationof a film derived from Mixture 4 was performed following similarprocedures as described in Example 6 to provide a crosslinked polymernetwork: wavelength of reflection=1325 nm.

Example 10

Mixture 5:

Compound 11 (0.023 g), Compound 25 (0.157 g), Compound 26 (0.078 g),Compound 27 (0.059 g), and IRGACURE 184 photoinitiator (0.006 g) werecombined and dissolved in DCM. The solution was filtered (0.45 micronfilter), and the solvent was removed to provide Mixture 5: phasebehavior: 1^(st) heating: X−30.1 TN*93.2 I; 1^(st) cooling: I 92.0TN*−29.0 X; 2^(nd) heating: X−27.5 TN*95.7 I. Coating and polymerizationof a film derived from Mixture 5 was performed following similarprocedures as described in Example 6 to provide a crosslinked polymernetwork: wavelength of reflection=1508 nm.

Example 11

Mixture 6:

Compound 11 (0.037 g), Compound 25 (0.157 g), Compound 26 (0.078 g),Compound 27 (0.059 g), and IRGACURE 184 photoinitiator (0.006 g) werecombined and dissolved in DCM. The solution was filtered (0.45 micronfilter), and the solvent was removed to provide Mixture 6. Coating andpolymerization of a film derived from Mixture 6 was performed followingsimilar procedures as described in Example 6 to provide a crosslinkedpolymer network. The film is hazy and has a broad reflection bandcentered around 1710 nm.

Example 12

This example demonstrates the stability of the polymer network of theinvention when subjected to a second coating of liquid crystal monomersolution. A separate batch of liquid crystal Mixture 1 was prepared andcoated onto a substrate and cured, as described in Example 6, to providea polymer network layer having a wavelength of reflection=610 nm. Anovercoating of the liquid crystal Mixture 1 was then coated onto thepolymer network layer, followed by drying and curing in a similar mannerto example 6, to provide a bilayer of a liquid crystal network,exhibiting a wavelength of reflection=608 nm. This indicated that theoptical properties of the polymer network from the first coating weresubstantially unaffected by the coating of the second liquid crystalMixture 1.

Comparative Example 1 Mixture A

Compound 28 (0.037 g), Compound 25 (0.157 g), Compound 26 (0.078 g),Compound 27 (0.059 g), and IRGACURE 184 photoinitiator (Ciba SpecialtyChemicals, Ardsley New York) (0.006 g) were combined and dissolved inDCM. The solution was filtered (0.45 micron filter), and the DCM wasremoved to provide Mixture A.

Coating and polymerization of a film derived from Mixture A wasperformed following similar procedures as described in Example 6 toprovide a crosslinked polymer network: wavelength of reflection=724 nm.This polymer network acted as the control film of Mixture A, andexemplified a polymer network having a chiral dopant that was notcovalently bonded to the polymer network

A overcoating of the liquid crystal Mixture A was then coated onto thepolymer network layer, followed by drying and curing in a similar mannerto Example 6, to provide a bilayer of a liquid crystal network,exhibiting a wavelength of reflection=715 nm. This indicated that thewavelength of maximum reflection of the polymer network from the firstcoating was shifted by 9 nm by overcoating liquid crystal Mixture A.

Example 13

This example demonstrates the stability of a polymer network of Mixture1 when subjected to an overcoating of liquid crystal monomer solutionMixture A. To a polymer network film provided by coating and curing ofMixture 1, as defined in Example 12, was applied an overcoating of theliquid crystal Mixture A, followed by drying and curing in a similarmanner to example 6, to provide a bilayer of a liquid crystal network,exhibiting a wavelength of reflection=610 nm (for Mixture 1 layer) and awavelength of reflection=714 nm (for Mixture A layer). As indicated inExample 12, Mixture 1 alone exhibited λ_(max)=610 nm. This indicatedthat the λ_(max) of the polymer network derived from Mixture 1 wassubstantially unaffected by the coating of the second liquid crystalMixture A.

Comparative Example 2

This example demonstrates the instability of a polymer network ofMixture A when subjected to an overcoating consisting of the liquidcrystal monomer solution Mixture 1. To a polymer network film providedby coating and curing of Mixture A, as defined in Comparative Example 1,was applied an overcoating of the liquid crystal Mixture 1, followed bydrying and curing in a similar manner to Example 6, to provide a bilayerof a liquid crystal network, exhibiting a wavelength of reflection=587nm (for Mixture 1 layer) and a wavelength of reflection=728 nm (forMixture A layer). As indicated in Example 12, Mixture 1 alone exhibitedλ_(max)=610 nm. This indicated that the λ_(max) of the polymer networkderived from Mixture 1 was substantially shifted as a result ofovercoating the liquid crystal Mixture 1 onto the polymer networkderived from Mixture A. Thus, it is clear that the polymer networkderived from Mixture A is acting as a source of chiral impurity in theovercoat of Mixture 1.

Each of the formulae shown herein describes each and all of theseparate, individual compounds that can be assembled in that formula by(1) selection from within the prescribed range for one of the variableradicals, substituents or numerical coefficents while all of the othervariable radicals, substituents or numerical coefficents are heldconstant, and (2) performing in turn the same selection from within theprescribed range for each of the other variable radicals, substituentsor numerical coefficents with the others being held constant. Inaddition to a selection made within the prescribed range for any of thevariable radicals, substituents or numerical coefficents of only one ofthe members of the group described by the range, a plurality ofcompounds may be described by selecting more than one but less than allof the members of the whole group of radicals, substituents or numericalcoefficents. When the selection made within the prescribed range for anyof the variable radicals, substituents or numerical coefficents is asubgroup containing (i) only one of the members of the whole groupdescribed by the range, or (ii) more than one but less than all of themembers of the whole group, the selected member(s) are selected byomitting those member(s) of the whole group that are not selected toform the subgroup. The compound, or plurality of compounds, may in suchevent be characterized by a definition of one or more of the variableradicals, substituents or numerical coefficents that refers to the wholegroup of the prescribed range for that variable but where the member(s)omitted to form the subgroup are absent from the whole group.

In this specification, unless explicitly stated otherwise or indicatedto the contrary by the context of usage, where an embodiment of thesubject matter hereof is stated or described as comprising, including,containing, having, being composed of or being constituted by or ofcertain features or elements, one or more features or elements inaddition to those explicitly stated or described may be present in theembodiment. An alternative embodiment of the subject matter hereof,however, may be stated or described as consisting essentially of certainfeatures or elements, in which embodiment features or elements thatwould materially alter the principle of operation or the distinguishingcharacteristics of the embodiment are not present therein. A furtheralternative embodiment of the subject matter hereof may be stated ordescribed as consisting of certain features or elements, in whichembodiment, or in insubstantial variations thereof, only the features orelements specifically stated or described are present.

All patents and patent publications cited herein are hereby incorporatedas a part hereof by reference.

What is claimed is:
 1. A compound as represented by the structure of thefollowing formula (I):D-S₁—(B—S₂)_(m)-(A₁S₃)_(n)—R_(p)  (I) wherein D is a chiral moiety (D1)or (D2) derived, by formal removal of a hydroxyl group, from thealkaloids selected from the group consisting of (−) cinchonidine, CAS[485-71-2]; (+)-cinchonine, CAS [118-10-5]; quinine, CAS [130-95-0] andquinidine, CAS [56-54-2]; and their dihydro-derivatives:

X is hydrogen or —OCH₃; R is —CH═CH₂ or —CH₂CH₃; S₁ is a linking groupselected from the group consisting of —O—, —OC(O)—, OC(O)NH and—OC(O)O—; S₂ and S₃ are linking groups each independently selected fromthe group consisting of, —C(O)—, —OC(O)—, —C(O)O—, OC(O)O, —OC(O)NR₁—,—NR₁C(O)O—, —SC(O)—, and —C(O)S—; R1 is hydrogen or C₁ to C₄ alkyl; eachB is a divalent radical independently selected from the group consistingof aliphatic and aromatic carbocyclic and heterocyclic groups having 1to 16 carbon atoms; optionally having one or more fused rings andoptionally mono- or polysubstituted with L; L is selected from the groupconsisting of the substitutents F, Cl, —CN, and —NO2; and alkyl, alkoxy,alkylcarbonyl, and alkoxycarbonyl groups, having 1 to 8 carbon atoms,wherein one or more of the carbon atoms are optionally substituted withF or Cl; A₁ is a divalent linear or branched alkyl having 2 to 20 carbonatoms, optionally interrupted by linking groups selected from the groupO, —S—, —C(O)—, —OC(O)— and —C(O)O—; R_(p) is a polymerizable group; mis an integer of 1 or 2; and n is an integer of 0 or
 1. 2. The compoundof claim 1 wherein —R_(p) is selected from the group consisting ofCH₂═C(R₂)—, glycidyl ether, propenyl ether, oxetane, and 1,2-, 1,3-, and1,4-substituted styryl and alkyl substituted styryl radicals, wherein R₂is hydrogen, Cl, F, or CH₃.
 3. The compound of claim 1 wherein n=0 and,the radical —S₂—R_(p) is CH₂═C(R₂)—C(O)—O—, and R₂ is hydrogen or —CH₃.4. The compound of claim 1 wherein n=1 and, the radical —S₃—R_(p) isCH₂═C(R₂)—C(O)—O—, and R₂ is hydrogen or —CH₃.
 5. The compound of claim1 wherein S₁ is —O— or —OC(O)—.
 6. The compound of claim 1 wherein S₁and S₂ are —OC(O)—.
 7. The compound of claim 1 wherein B are eachindependently divalent radicals selected from the group consisting of1,4-cyclohexyl; 2,6-naphthyl; 4,4′-biphenyl; andR₁₁-substituted-1,4-phenyl, wherein R₁₁ is H, —CH₃ or —OCH₃.
 8. Thecompound of claim 1 wherein formula (I) is selected from the groupconsisting of formula (IIa), (IIb), (IIc) and (IId):

wherein R₁₁ is H, —CH₃ or —OCH₃; and R₂ is hydrogen, Cl, F, or CH₃. 9.The compound of claim 1 wherein formula (I) is formula (IIIa) or (IIIb):

wherein R₂ is hydrogen, Cl, F, or CH₃.
 10. The compound of claim 1wherein formula (I) is formula (IVa) or (IVb):

wherein R₁₁ is H, —CH₃ or —OCH₃; A₁ is a divalent linear or branchedalkyl having 3 to 20 carbon atoms, optionally interrupted by linkinggroups selected from the group O, —S—, —C(O)—, —OC(O)— and —C(O)O—; andR₂ is hydrogen, Cl, F, or CH₃.
 11. A polymerizable liquid crystalcomposition comprising at least one compound of claim
 1. 12. Thepolymerizable liquid crystal composition of claim 11 further comprisinga compound of formula (V):

wherein R₂ is independently selected from the group: H, F, Cl, and CH₃;n1 and n2 are, independently, integers 3 to 20; u and v are,independently, integers 0, 1 or 2; A is a divalent radical selected fromthe group:

wherein R₃-R₁₀ are independently selected from the group: H, C₁-C₈straight or branched chain alkyl, C₁-C₈ straight or branched chainalkyloxy, F, Cl, phenyl, —C(O)CH₃, CN, and CF₃; X₂ is a divalent radicalselected from the group: —O—, —(CH₃)₂C—, and —(CF₃)₂C—; and each B₃ andB₄ is a divalent radical independently selected from the group:2,6-naphthyl; 4,4′-biphenyl; and R₁₁-substituted-1,4-phenyl, wherein R₁₁is H, —CH₃ or —OCH₃; with the proviso that when the sum of u+v is equalto 3 or 4, at least two of B₃ and B₄ are R₁₁-substituted-1,4-phenyl. 13.The polymerizable liquid crystal composition of claim 12 wherein, withinformula (V), u is 1 and v is 0, and formula (V) is formula (VIa):

wherein R₂ is independently H or CH₃; R₃-R₆ are independently H or —CH₃;and B₃ is R₁₁-substituted-1,4-phenyl, wherein R₁₁ is H, —CH₃ or —OCH₃.14. The polymerizable liquid crystal composition of claim 12 wherein,within formula (V), u and v are 1, and formula (V) is formula (VIIa):

wherein R2 is independently H or CH₃; R₃-R₆ are independently H or —CH₃;and B₃ and B₄ are R₁₁-substituted-1,4-phenyl, wherein R₁₁ is H, —CH₃ or—OCH₃.
 15. A polymer network polymerized from the composition of claim11 or
 12. 16. The polymer network of claim 15 having a wavelength ofmaximum reflection in the range of about 280 to about 2500 nm.
 17. Thepolymer network of claim 15 having a wavelength of maximum reflection inthe range of 700 to about 1400 nm.
 18. The polymer network of claim 15that is an optical element.